Prefabricated shell concrete structural components

ABSTRACT

A concrete shell is formed as a mold for substantial concrete structures. The shell includes an interior mesh element that will be encapsulated in concrete in the poured concrete structure. A panel of moisture impervious material forms an outer layer of the concrete shell and acts as a form for field poured concrete making up a structural concrete element.

CROSS REFERENCE TO RELATED APPLICATIONS

This is an original application not related to any other applications.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to forms used for in situ casting of concrete products such as, but not limited to piers, columns, beams and concrete elements of highway overpasses, long span bridges, docks and piers, train bridges, parking garage structures, raised streets and highways and similar large structural components.

2. Description of Related Art

No concrete structures using the type of prefabricated shells presented in this disclosure, having the configuration of components herein disclosed or relying on the method used in making structures as taught herein, are known. There exists concrete forms for making structural concrete components and there are concrete forms that are precast, shipped to a construction site, and then filled with concrete on site. U.S. Pat. No. 6,189,286 B1 discloses a fiber tube that is formed at a remote manufacturing location and shipped to a construction site. The fiber form is then filled with concrete at the site. The form, being of fiber reinforced material, has advantages, such as impermeability to water and chemicals, however the completed product is different from the structure presented herein in that in the known invention, the fiber reinforced form becomes the exterior surface of the finished product. In the invention herein a fiberglass panel becomes the inner panel of a shell and the shell is then filled with concrete. Thus the fiberglass panel is encased in concrete in the final configuration. Another patent disclosing a form for concrete filling at a construction site is shown in U.S. Pat. No. 3,678,815. This patent discloses a precast, field-filled structure, however, even this patent does not disclose the invention set forth herein. For instance, the '815 patent teaches away from the instant invention in that it discloses a structure that has two clamshell like premolded shell pieces, which are assembled one-to-the-other at the jobsite, rather than the single prefabricated shell mold that is disclosed herein. Furthermore, the '815 patent teaches the use of welded mesh wire fabric in the field filled structure. This is contrary to one object of this invention, that being that the completed structure is designed to avoid, or at least to minimize, the use of ferrous metal products that will oxidize and cause deterioration of the structure.

U.S. Pat. No. 5,032,197 discloses a manhole repair technique where a plastic liner is spaced away from a deteriorated wall surface of the manhole. Concrete is poured into the zone between the old wall and the liner. The liner may be held in place by interlocking T-ribs until the concrete is poured. This is not a system for the manufacture of a prefabricated shell structure that is eventually filled as is taught by this disclosure.

SUMMARY OF THE INVENTION

The idea presented herein is apparatus and a method of casting major structural components out of concrete. The apparatus is a structure that is manufactured in a controlled environment and then shipped to a final location where the structure is permanently placed and subsequently filled with a concrete mix to form a structural component of significant size. The manufactured precast or prefabricated structure, referred to as shells or prefabricated shells in this disclosure, is both the form for containing the significant mass of concrete provides load supporting and bearing strength to the finished structure and a structural portion of the final structural product such as pier, column, arch, bend cap, bridge, elevated roadway support, and the like.

The prefabricated shells will use a carbon fiber mesh grid, or welded wire mesh grid equivalent, instead of a conventional welded wire mesh grid. The preferred embodiment of the invention will not incorporate steel or any other materials susceptible to corrosion in the precast concrete components. Even epoxy or plastic coated steel mesh grid is subject to corrosion if the epoxy coating is compromised, which is easily done in handling and positioning of a welded wire mesh grid. A carbon fiber mesh grid is chemically inert and non-corrosive.

The carbon fiber mesh, being inert, is not subject to corrosion, can be positioned in the prefabricated shell close to what will become the outer surface of the shell. This will reduce surface cracking of the shell as the reinforcing carbon mesh will be closer to the outside surface than is practically possible in a formed-in-place concrete structure of a conventional reinforced structure where the reinforcement elements, the rebar, for instance, cannot be too close to the surface as it would be subject to moisture penetration and ultimately oxidation and rusting of the metal reinforcement elements. In the case of the prefabricated shells themselves the carbon mesh will provide structural strength to carry the dead load of the unfilled prefabricated shells as the shells are being transported from the production factory to the job site where the prefabricated shells will be filled with concrete.

One technique of on-location filling and pouring of concrete structures involves the well-known use of wooden or metal forms. The forms are installed at the site, the concrete is poured into the forms and after the concrete cures the forms are removed and trucked to storage for a subsequent use. There are significant costs in the transportation of the forms, the erection of the forms and the removal of the forms. The development herein provides a method of pillar and beam construction that reduces the use of temporary formwork and thus the labor costs to transport, position and remove the temporary forms.

It is the inventor's intention to provide a system that is used to create structural concrete elements such as bend caps, beams, piers and columns, wherein the finished products are impervious to the effects of chloride-ion migration, internal steel corrosion, imperviousness to the effects of alkali-silica reactivity, and the effects of freeze-thaw cycles in cold climates. The resulting structure will resist detrimental expansion and contraction effects and surface cracking of the completed column or beam. For instance, since the prefabricated shell includes a fiberglass or, alternatively, a high-density polyethylene (HDPE) panel comprising the inner surface of the shell, it can be configured to provide a mechanical bond between itself and the concrete poured into the shell at the job site. This is advantageous as the shell is now somewhat a sacrificial barrier to absorb abuse from impacts on the finished structure. In actual use the prefabricated shell can deteriorate from external contamination or it can be destroyed by impacts. However, the inner wall, the fiberglass panel for example, and the core concrete structure will stay intact. The prefabricated shell is thus repairable or resurfaceable without the need to replace or repair the core concrete structure. Furthermore, the repair can be made without compromising the corrosion protection provided by the inner wall structure.

Another feature of concrete structures using the techniques of the prefabricated shells set forth herein, is that the structure can accommodate different rates of thermal expansion, contraction and deflection between the interior concrete core, that core being poured at the job site, and the prefabricated shell which usually be fabricated at a remote location.

By using a system where the forms are prefabricated shells, and by using silica-fume additives discussed further on in the manufacture of the prefabricate shells, the prefabricated shell as well as the final concrete structure is resistant to load transfer fracturing. This and some of the advantages set forth above and in the following specification provides a method of construction and an actual structure that has a longer life cycle and a higher structural integrity than conventional methods of forming completed concrete structures.

An advantage of using the additive, such as silica-fume, in the prefabricated shell, rather than in the entire concrete structure, is that the overall cost of each structure can be reduced as the additive need only be mixed into the prefabricated shell, not mixed into the concrete of the entire column, in order to yield the results desired from this invention.

In conventional on-site form filling the forms are not normally part of the structure. They are simply containment barriers that are removed once the concrete has been poured and cured. Since the conventional forms don't make up part of the completed structure the amount of concrete poured into a conventional form system for a similar sized component is greater than the amount of concrete poured into the prefabricated shells taught by this disclosure. This is significant conventional forms are limited by the volume that they can accommodate before “blowing” out. For instance, a four foot diameter conventional form for a column can only be made about twenty feet tall. If it is filled in one pour the form will be approaching its ability to maintain its integrity without blowing out. The conventional form can have auxiliary shoring and bracing but this adds cost and time in to the assembly and disassembly of the conventional form. Thus the number of lift limitations, a “lift” being when forms are set up, poured, cured, stripped, and moved and set up again, is partially determined by the temporary framework's capacity and the complications in forming a base, integrating it with a pier or column, and then to a bent cap. To make a forty foot tall column two lifts of twenty feet each would be needed. Also, there is an economic limit of providing temporary formwork for the entire structure at one time without reusing forms. For these, and other reasons known in the industry, this means that there are a limited number of lifts for a large structure. A large number of lifts may yield a higher percentage of cold joints in the completed structure. With this invention the number of lifts is reduced significantly as the prefabricated structures can be stacked on top of each other, for instance a twenty foot column form can be stacked on a twenty foot column form making a forty foot column that can be poured in one pour without blowing out the prefabricated shells.

Since the prefabricated shell is formed at a factory site curing conditions can be controlled carefully by the fabricator. The shell curing cycle is observable, testable, predictable and therefore engineerable to ensure a consistent and uniform prefabricated shell. The system presented here is more efficient in that the forms are made of the prefabricated shells, there is no need to transport and manipulate removable forms and the resulting product is impervious to water intrusion and the attendant corrosion and structural deterioration.

An object of the invention, in addition to the objects and advantages set forth above, is to provide a method of forming a prefabricated shell, and the shell itself, that layers protective elements in a way that is not done in the industry. The layering creates a prefabricated shell and concrete structure that has its own internal protective layer provided by the mechanical fastening of a fiberglass layer as part of the prefabricated shell. This layer becomes an internal barrier in the completed concrete filled structure.

One advantage of the structure is that there are sealed joints between the components that block water, air, and chloride-ion migration through the joint to the concrete and steel structure.

By using the method and the components set forth herein the resulting structure possesses at least two important advantages over the art. These include, but are not limited to, corrosion protection on the exterior of the final concrete structure and increased compressive strength in the core of the finished product. It is also advantageous in that the structural steel reinforcements, such as reinforcement bar (“rebar”), can be arranged near the edge of the core structure without the risk of these steel elements being subjected to corrosive elements from moisture intrusion as there is a fiberglass or plastic barrier on the inside of the prefabricated shell. By placing the rebar closer to the outer surface of the structure the efficiency of the reinforcing bars is increased. This is possible in this invention as the rebar remains protected from contaminating environmental elements.

The above summary does not include an exhaustive list of all aspects, advantages or objects of the present invention. The inventor contemplates that his invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the detailed description below and particularly pointed out in the claims. Such combinations have particular advantages not specifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention, including the inventor's preferred embodiment, are presented here and are described below in the drawing figures and Detailed Description of the Drawings. Unless specifically noted, it is intended that the words and phrases in the specification and the claims be given the ordinary and customary meaning to those of ordinary skill in the applicable arts. If any other special meaning is intended for any word or phrase, the specification will clearly state and define the special meaning.

FIG. 1 is an illustrative elevation view of a precast column having a portion removed to reveal the internal structure of the column,

FIG. 2 is a broken away portion of the exposed interior of the column shown in FIG. 1,

FIG. 3 is a sketch of a portion of an prefabricated shell column from the end of the column,

FIGS. 4 A-D show three stages in the formation of a tubular shaped prefabricated shell,

FIGS. 5 A-D show three stages in the formation of a rectangular open-topped shaped prefabricated shell,

FIG. 6 is a truncated cross sectional presentation of a pier or column,

FIG. 7 shows a broken away portion of a structural beam prefabricated shell,

FIG. 8 is a complete top view of the structure of FIG. 7,

FIG. 9 is cross-sectional view of FIG. 8 taken through 9-9,

FIG. 10 is a partial side elevation pictorial representation showing post tensioning hardware,

FIG. 11 is an end view of the structure of FIG. 10,

FIG. 12 is a pictorial representation of a portion of a set of two interlocking forms,

FIG. 13 is a pictorial representation of the components of FIG. 12 post pour,

FIG. 14 is a representation of a cross sectioned view of a concrete structure poured monolithically inside prefabricated shells,

FIG. 15 is a cross sectioned view of a lid for an open pour section element,

FIG. 16 is a cross sectioned view of a portion of a lid and pour section element.

DISCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

In the following figures like reference characters indicate like components.

Looking first at FIG. 1, one embodiment of the invention is shown. In this figure a pier or column, generally 10, is shown with a portion of the surface removed to show the internal structure of a completed precast, field-filled concrete column. The outer layer 12 of the column, comprised of concrete, is finished with a smooth finish. The finish on surface 14 is a smooth metal form finish that is imparted to the concrete outer layer 12 through contact with the metal form in which the prefabricated shell is initially cast. The prefabricated shell 16, as shown in FIG. 1, is generally a hollow shell tubular structure of any of many cross-sectional shapes, such as, but not limited to, circular, square, oblong, rectangular, obround, triangular, multiplanar, or the like, cross sectional shapes. The prefabricated shell 16 will be filled in the field with an appropriate concrete as determined by structural parameters.

In FIG. 2, a broken away portion of the column shown in FIG. 1, the interior details are more readily visible. The prefabricated shell 16 comprises a concrete shell and cast in the concrete of this shell is a non-reactive reinforcement grid sheet of material 20 that is located and supported in place by spacers or locators, one shown as 22. The non-reactive reinforcement grid sheet of material in one embodiment is a non-metallic, screen-like material of carbon-based, polymer-based, or plastic derived material, such as, but not limited to, polystyrene, polyethylene, polypropylene, or other man-made fibrous spun, extruded or woven products. In other embodiments it may be advantageous to make the non-reactive reinforcement grid material, or welded wire mesh grid equivilent, of carbon tows or naturally occurring materials such as, but not limited to mineral products, such as silica-based products such as glass; plant fibers; or even animal fibers. One other embodiment may rely on the use of metallic content screen, such as stainless steel or moisture barrier encapsulated steel, each falling under the general broad term of a welded wire mesh equivalent. Such metallic content screen would best meet the inventor's intent of incorporating non-oxidizing materials in the prefabricated shell if the metallic comprising material were impervious to oxidation due to moisture or exposure to chemicals.

One embodiment of the invention contemplates the use of “C-Grid” Brand Carbon Grid for concrete reinforcement material made by bonding ultra high-strength carbon tows with epoxy resin in a controlled environment. This product is available from TechFab, LLC of Anderson, S.C.

The spacers, or hereinafter, the locators 22 are attached to the non-reactive reinforcement grid material 20 at junction 24. The spacers will assist in locating the non-reactive reinforcement grid material appropriately in the prefabricated shell 16.

The interior surface of the prefabricated shell 16, that is, the surface that will contact the concrete that is poured into the prefabricated shell in the field, is comprised of a fiberglass panel 26 with, in one embodiment, a polyester resin surface coat. The fiberglass panel 26, or as an alternative material, the panel would be high density polyethylene or other suitable plastic or polymer material, is generally continuous, although it may have seams, preferably watertight seams, where a panel will overlay an adjacent panel, as one of its purposes is to act as an interior form, as well as an interior structural element of the prefabricated shell 16. The fiberglass panel may be of 16-ounce/square foot fiberglass or any other weight of fiberglass material that is structurally appropriate for particular purposes. As shown in FIGS. 2, 3 and 13, it is desirable to provide surface features such as protrusions 28 on the interior surface of the fiberglass panel 26. These protrusions provide mechanical bonds between the fiberglass panel 26 and the cured concrete that fills the prefabricated shell in the field. These protrusions 28 can be of any shape and in an alternative embodiment can be indentations or a surface pattern that will provide an attachment capability between the interior of the fiberglass panel and the field poured concrete. Note that the protrusions in FIG. 13 are “T-shaped” nibs, a preferred embodiment, different then the protrusions shown in FIGS. 2 and 3, simply to show that there are different configurations of protrusions, not just those shown in the drawing figures, which are contemplated by the inventor. The mechanical bond between the panel and the poured concrete is desirable, as it will assist in maintaining continuity between the fiberglass panel and the field poured concrete and a fluid impervious barrier protecting the concrete. This is helpful in the event that the preformed shell is compromised once installed, such as by an impact from a vehicle hitting a bridge column, or in a less dramatic situation, by maintenance equipment, such as a mover or a snow plow blade hitting the base or a column.

As mentioned above, an alternative to the fiberglass panel is the use of a high-density polyethylene material (HDPE), or for that matter, other polymer based products, for the inner wall structure. HDPE is often used in underground water and sewer systems as it is lightweight and highly resistant to chemical corrosive attack.

The panel 26 functions primarily as a separation layer, both as a mechanical barrier and as a thermal break or barrier, between the prefabricated shell and the poured at the job site concrete core. The panel 26 is not intended to accept structural load transfer, although it is significant enough to resist the pressure of the concrete poured around it during the fabrication stage of the formation of the prefabricated shell. The utility of the barrier is realized early on at the job site where it helps create an ideal concrete curing environment by not only providing for an even temperature during the curing process due to the thermal break, but also prevents dehydration of the “wet mix” concrete that is poured into the prefabricated shell at the job site by blocking water migration from the mix to the prefabricated shell. That is, without the panel 26, the water in the concrete mix would be absorbed into the prefabricated shell and thus adversely affect the cure of the wet mix concrete. This panel 26 creates a protective envelope around the concrete core and the reinforcing steel generally positioned in the concrete core. The panel is a barrier to chloride-ion migration, moisture and air. As mentioned above, the panel enables the prefabricated shell to be damaged and repaired, or even deteriorate, without the need of repairing the concrete core of the pier, column, beam, bent cap, truss, or the like.

The locators 22 mentioned above are also attached to the fiberglass panel 26 such that the locators 22 extend inboard into the interior of the prefabricated shell and connect to, or locate, the non-reactive reinforcement grid 20.

The concrete material of the prefabricated shell, in one embodiment, is silica-fume four thousand pound concrete. It is preferred that class-X type four thousand pound or better gray cement is used in the material of the prefabricated shell. Silica-fume concrete is a high performance concrete product that is regular gray concrete augmented through the addition of silica-fume. Silica-fume, a byproduct of producing silicon metal or ferrosilicon alloys, is highly resistant to penetration by chloride ions. It is primarily amorphous silicon dioxide and its particle size is 1/100^(th) the size of an average cement particle. It is a reactive pozzalon (pozzalon is a siliceous or siliceous and aluminous material that possesses little or no cementitious value. In a finely divided form and in the presence of moisture, however, pozzalon reacts chemically with calcium hydroxide to form compounds possessing cementitious properties.) Concrete containing silica-fume can have very high strength and can be very durable. Silica-fume makes concrete watertight and corrosion resistant in marine applications and de-icing salt applications. Thus its use in piers, bridge columns, bent caps, bridge spans and other structural applications exposed to rain, snow, and deicing chemicals along roadways meets the inventor's objective of providing a long-lasting, weather resistant and highly corrosive resistant product.

Another concrete additive that can be used in the manufacture of the prefabricated shell is ground granulated blast furnace slag. This, and the silica-fume additive, are both helpful in reducing or eliminating the migration of chloride-ions, moisture, and gas migration to the structural reinforcing members embedded in the completed structural field-poured elements. These additives will also create higher compressive strength in the prefabricated shell.

The use of the silica-fume or other concrete additive in the prefabricated shell eliminates the need to use silica-fume additive, or another performance enhancing additive, in the wet mix that is poured into the prefabricated shell. This is a significant cost savings as the additives are expensive and the use of the additives throughout the entire structure, rather than just in the shell, does not add significant functionality to the finished field-poured concrete structure.

The concrete mixture for the prefabricated shell is, preferably, a self-compacting concrete mix (SCC).

The concrete of the prefabricated shell may include a color additive so that a uniform and pleasing color is impregnated into the concrete. This color will last longer than paint on concrete. Balanced and even hue and intensity of color between separately cast prefabricated shell components can then be achieved thus a set of components will be uniform and otherwise match each other in color and surface treatment.

The non-reactive reinforcement grid material 20, in one embodiment of the invention where the thickness of the prefabricated shell is on the order of four inches thick, is supported approximately three inches away from the interior surface of the fiberglass panel 26 by the locators 22. The non-reactive reinforcement grid will be about one inch inboard from the exterior surface 12 of the prefabricated shell. Thus, in this embodiment mentioned above, the wall thickness of the prefabricated shell will be approximately four inches thick depending on the thickness of the fiberglass panel. Of course prefabricated shell thickness could be selected to be in a range of from very thin, perhaps less than an inch thick, to much thicker than four inches.

Generally, the exterior surface of the prefabricated shell will be a smooth surface resulting from the surface of the mold being smooth. It is possible, and probable in many situations, that the exterior surface of the prefabricated shell is cast with architectural relief, stylized relief and contours, or designed to match existing structures. In this regard, it appears that factory precast concrete can more easily and conveniently yield cost effective designs, or at least designs that are more cost effective than temporary form work. The prefabricated shells can become quantity production pieces with standard compatible shapes and sizes for mass production and quick short lead time on order delivery.

FIG. 3 is an end view of a column represented by a sketch showing a portion of an prefabricated shell before the prefabricated shell is completed by filing it with silica-fume concrete. In this view the fiberglass panel 26 shows the locators attached to it, the non-reactive reinforcement grid 20 attached to the inboard end of the locators 22, and the exterior surface of the prefabricated shell 12 shown as a dotted line as the prefabricated shell has not been completed with a filling of silica-fume and concrete mix. The three radius lines, a, b, c, show the distance from the center of this tube shaped column. The lines represent the exterior 12, the non-reactive reinforcement grid 20 and the fiberglass panel 26 and show how far, relatively, they are from the center of the column. For instance, the non-reactive reinforcement grid, or welded wire mesh equivalent, is located closer to the exterior surface 12, than it is to the internal surface of the panel 26. For example, the non-reactive reinforcement grid 20 is supported by the locators 22 to be approximately three inches away from the panel 26 and about one inch away from what will become the exterior surface of the prefabricated shell. Precise location of the non-reactive reinforcement grid is not critical, it is however suggested that the non-reactive reinforcement grid not be flush against either the fiberglass or other moisture impervious panel or the exterior of the prefabricated shell when it is completed.

FIGS. 4 A-D is a series of sketches that show the acts followed in making a prefabricated shell of a generally circular cross-section shape. If this were a pier or column of square cross-section, or any other closed cross-section, the acts would be similar if not the same. One act is to prepare the fiberglass panel 26. The panel is formed into a tubular structure as shown and the surfaces, both inside 30 and outside 32 surfaces, (the “outside surface” has been referred to as the “interior surface” previously, and it will be further on, as it is the interior surface of the completed prefabricated shell) are prepared for the next acts in the process of making the prefabricated shell. For instance, the inside surface 30 may be coated with a product, or with protrusions such as 28, that enhances the strength of the mechanical interface between the inside surface of the fiberglass panel and the concrete that will eventually be poured into the prefabricated shell in the field. The outside surface of the fiberglass panel 26 may also be prepared with a surface treatment that will enhance, but not bond tightly together, although a tight bond is an option, the interface between the fiberglass panel and the silica-fume containing concrete used in the formation of the prefabricated shell.

FIG. 4B shows, in a sketch, the location of the non-reactive reinforcement grid 20 spaced away from the surface 32 by use of the locators (FIG. 2) which are attached to the surface 32 and to the non-reactive reinforcement grid 20, in this case, several inches away from the surface 32.

Another act in making the prefabricated shell is shown in FIG. 4C wherein a mold 34, half of a multipart mold shown in this figure, is positioned or assembled around the structure shown in FIG. 4B. The mold 34 can be assembled around the fiberglass panel and the non-reactive reinforcement grid or the fiberglass panel and non-reactive reinforcement grid can be inserted into a multipart mold, such as multipart mold 34, or alternatively, a unitary mold, not shown. The function of the mold 34 is to contain the silica-fume concrete mixture from flowing away from the fiberglass and non-reactive reinforcement grid assembly until the concrete mixture has at least set up, or more typically, has cured in a controlled manner.

Note that in the acts of forming the prefabricated shells here, there is no need to use the conventional “mold and plug” method of shell formation, as no “plug” is required in this method of manufacture.

As shown in FIG. 4D the act of filling or “pouring,” the prefabricated shell with a silica-fume concrete mixture 36 is complete. The concrete 36 has been poured into the mold 34 and fills the area between the mold surface. In a preferred embodiment, the surface on the final prefabricated shell exterior surface 14 in FIG. 1, will be a smooth surface due to contact with the smooth finish interior of the mold. Alternatively, the interior of the mold can be finished in a surface having a non-smooth surface and even a surface with design character, such as brick shapes in relief, formed thereon.

After the prefabricated shell concrete has cured, or before thorough curing, the mold will be removed from the now completed prefabricated shell. In one embodiment the exterior surface 12 will be spaced about an inch away from the now concrete encapsulated non-reactive reinforcement grid 20 located by the locators 22. There will be several inches of concrete, preferably a four thousand pound or higher class X concrete, between the non-reactive reinforcement grid 20 and the interior of the fiberglass panel 26. The panel 26 becomes a part of the prefabricated shell and is not removed but becomes a barrier between the shell and the concrete core.

To summarize, the manufacturing acts in the prefabrication of the shell include the acts of: preparing an inner wall structure, this being a fiberglass or plastic panel; positioning a carbon fiber grid at a spaced distance around the inner wall structure using locators or spacers as positioning elements; either placing the inner wall structure with the fiber grid in a mold or else building a mold around the inner wall structure and fiber grid; filling the space between the mold surface, which can be a metal, wood, natural or synthetic surface appropriate for imparting a desired finish to what will become the outside surface of the prefabricated shell, and the interior surface of the inner wall structure; curing the augmented concrete in the mold and then removing the prefabricated shell from the mold once it is cured. One additional act may also be performed in the shell fabrication process. That act is the setting of lifting pin receivers and lifting pins, as appropriate, in the mold cavity before the cavity is filled with the silica-fume concrete mixture. These lifting pins will be used for lifting the prefabricated shell at various handling stages before the shell is finally field filled with concrete. Furthermore, non-corrosive inserts can be cast into the shells to accept a heavy duty bolt, or bolts, for lifting, shoring, bracing, or material handling purposes.

FIGS. 5 A-D are very similar to the FIG. 4 series of figures but show a rectangular open top box-like structure that will normally be used as a spanning, bridging, bent cap, or truss-like support at the construction site. The FIG. 5 embodiment is one embodiment of the invention, however, many other shapes of open top prefabricated shells, that is prefabricated shells that are box-like structures that are rectangular, square, multisided, round, oval, or the like, that are intended to be filled through the open top with concrete at the job site once the prefabricated shell is positioned or staged for installation, are contemplated by the inventor. One act in the series of acts shown in FIG. 5 is to prepare the fiberglass panel 26. This panel, similar in composition to the previously mentioned fiberglass panels, is formed into a box-like structure as shown in FIG. 5A and the surfaces, both inside 30 and outside 32 surfaces, (the “outside surface” has been referred to as the “interior surface” previously, and it will be further on as well, as it is the interior surface of the completed prefabricated shell) are prepared for the next acts in the process of making the prefabricated shell. The surfaces of the fiberglass panels are treated as above.

FIG. 5B shows, as a sketch, the location of the non-reactive reinforcement grid 20 spaced away from the surface 32 by use of the locators (FIG. 2) which are attached to the surface 32 and to the non-reactive reinforcement grid 20, in this case, several inches away from the surface 32.

A further act in making the prefabricated shell for the open top structure is shown in FIG. 5C wherein a mold 34, a portion of a multipart mold shown in FIG. 5C, is positioned or assembled around the structure shown in FIG. 5B. The mold 34 can be assembled around the fiberglass panel 26 and the non-reactive reinforcement grid or the fiberglass panel and non-reactive reinforcement grid can be inserted into a multipart mold, such as multipart mold 34 shown in FIG. 5C, or alternatively, a unitary mold, not shown.

As shown in FIG. 5D the act of filling the void between the prefabricated shell with a silica-fume concrete mixture 36 is complete. The concrete 36 has been poured into the mold 34 and fills the area between the mold surfaces. In a preferred embodiment, the surface on the final prefabricated shell exterior surface 14 in FIG. 1, will be a smooth surface due to contact with the smooth finish interior of the mold 34. Alternatively, the interior of the mold 34 can be finished in a surface having a non-smooth surface and even a surface with design elements, such as contour shapes in relief, formed thereon.

As stated above with respect the pier or column prefabricated shell shown in FIG. 4, after the concrete poured into prefabricated shell has cured, or before thorough curing, the mold 34 will be removed from the now completed open top box-like prefabricated shell. The panel 26 becomes a part of the prefabricated shell and is not removed under normal circumstances. It becomes the innermost surface of the prefabricated shell and is the surface that will be in contact with the concrete that is poured into the shell at the construction site.

FIG. 6 shows a cross sectional view of a pier column generally 38 illustrative of a prefabricated shell structure that has been field-filled with concrete. The prefabricated shell comprises the fiberglass panel 26, the locators 22, the non-reactive reinforcement grid 20, and the silica-fume containing concrete structure 36, all of which make up the form. In this FIG. 6 depiction the prefabricated shell is filled with concrete 40 showing a completed column, as it would be completed at a construction site. This embodiment includes an optional structure support lip 42 in the vicinity of the top of the pier or column as well as an optional depth limiting lip 44 near the bottom of the column. Since the prefabricated shell comprises silica-fume augmented cement the structure support lip 42 and the depth limiting lip 44 will have properties similar to the strength properties of the main section of the prefabricated shell.

Also shown in FIG. 6 is a base element 46 including relief or pocket 50 that will accept the base of the pier column 38. Similarly, a truss structure 52 has a relief or pocket 54 that will accept the upper end of the column 38. The column 38 will support the truss structure 52 primarily through the bent cap or truss structure 52 bearing on the top of the column rather then having the structure support lip 42 supporting the weight of the truss structure 52. The bottom of the column 38 will rest on the floor of the cavity 50 so that the weight of the column 38 and any load it is supporting is taken by the base of the column 38 and the base element 46 rather than the depth limiting lips 44.

One embodiment of a prefabricated shell for the construction of a base element 46 is shown in FIGS. 7-9. In FIG. 7 a prefabricated shell for a base element is shown having walls such as 54 integral with a top 56. The top 56 has through apertures that will, after the prefabricated shell is filled with concrete, form the pockets 50 shown in FIG. 6.

The interior of the prefabricated shell 46 comprises the fiberglass panel 26 as discussed above in the description of the column shells. The fiberglass panel is shown as a dotted line in FIG. 8 and is clearly shown in FIGS. 7 and 9. The structure of the prefabricated shell includes the fiberglass panel 54, the locators 22 and the non-reactive reinforcement grid 20 as pictorially depicted in FIG. 9. Not shown in any of these three views is the external, removable mold, similar to the mold 34 shown in FIGS. 5C and 5D. The mold for this base unit will be slightly more complicated than the mold shown in FIGS. 5C and 5D as there are radiused ends rather than the square ends in FIG. 5. The principle of filling the void between the fiberglass panel 54 and the mold with silica-fume concrete is the same as is discussed above. This also includes the inclusion of the non-reactive reinforcement grid sheet of material 22 spaced away from the fiberglass plates 26 through the use of the locators 22.

It should be pointed out that the use of silica-fume additive is one embodiment contemplated by the inventor. It is, of course, possible to use other concrete property enhancing additives, such as but not limited to ground granulated blast furnace slag, or the like.

The base element or prefabricated base shell will be shipped in the form shown in FIG. 7 to a job site where it will be positioned and then filled with concrete of the design engineer's specification. With this base unit in place and filled, the next act, if the base is being used as a support for a column, is to position prefabricated shell columns in the pockets 50 and then fill the columns with concrete. Alternatively, the columns can be placed before any concrete is poured into the base unit. After the columns are placed in the base unit, and supported thereon by the depth limiting lips 44 of FIG. 6, concrete can be poured into the columns and the base unit in a single operation.

The prefabricated shell FIGS. 7-9 is described above as a base unit. The same structure can be used as a bent cap or truss structure such as item 52 of FIG. 6, if it is inverted. The forming of the truss structure 52 is as described above but the prefabricated shell is inverted when placed on the columns, generally being supported by structure support lips 42 of FIG. 6.

FIG. 10 shows an embodiment of the invention having post tension strands 60 inserted in the prefabricated shell 16. As seen in FIG. 11, the end of the prefabricated shell 16 is provided with sleeves, such as 64, through the face or side of the prefabricated shell. Locking assemblies such as 62 are placed to interface with the post tension strands 60. The locking assemblies and the sleeves do not compromise the integrity of the shell and it remains watertight and highly resistant to fluid contamination, such as chloride slurry resulting from melting ice, melted from chloride applications, on roadways.

FIGS. 12 and 13 illustrate a vertical joint between two stacked prefabricated shells, a lower shell 66 and an upper shell 68. A watertight connection is made between the two stacked shells by use of bituminous mastic joint compound 70, which is positioned on an upper ledge 72 at an upper location on the lower shell. A spacer, here a stack of adjustment shims 74, are stacked on a low ledge 76 of the upper location of the lower shell 66. A lip or flange 80 will come into play when the upper stacked shell 68 is lowered onto the lower stacked shell 66. This is shown in FIG. 13 wherein the upper shell is positioned in its final position on the lower shell. The pressure exerted between the upper and the lower shells during assembly compress the bituminous mastic causing it to form a water tight seal between the upper and lower shells. It is kept from flowing into the interior of the shells by the lip or flange 80 as can be seen in FIGS. 12 and 13. The final position is accomplished when the shells are filled with concrete and the shim stack 74 is removed. An expending void foam filler material 82 is injected into the joint between the lower and the upper shells. A foam backer rod 88 separates the filler material 82 from caulk material. The remaining crevice is filled with a caulk compound 84 such as “Sika-Flex” brand caulk. The expanding foam will assist in preventing water, vapor, or chloride-ion migration through the joint void to the interior concrete. The Sika-Flex, or other caulking system, assists in bonding the shells to the expanded foam filler. At this point, that is, after the shells are filled with concrete, the concrete core becomes the supporting structure of the finished pier or column.

FIGS. 12 and 13 show the placement of a representative plastic insert 102 that may be cast into the shell. The insert 102 is provided to accept a bolt, such as 104, or other similar lifting, shoring, bracing, or supporting fixture that is inserted into the insert 102 for the use of lifting, shoring, bracing, or support. For instance, in FIG. 13, a support link 106 can be bolted to the shell by the bolt 104 passing through an aperture in the support link 106 into the threaded, non-corrosive insert. The non-corrosive insert will prevent the bolt from providing a moisture path to the inside of the shell. When the bolt is removed, for instance, if it is a temporary placement for supporting or aligning the shell, the insert 102 may be filled with caulk, covered with an end cap or both. In some instances, it may be unnecessary to fill the plastic insert as there may be no concern about moisture entering the shell through the insert 102. Generally, the insert 102 will not penetrate deeply into the shell and thus there is reduced chance that contamination can traverse the shell and get into the shell or the concrete that is poured into and fills the shell.

Another use for the insert 102 is to accept a more permanent shoring rod, not shown, that would extend from in the insert to a locator that accepts the other end of the locator. The locator could be, for instance, secured to the ground, secured to a nearby structure, or to another part of the same structure to provide bracing, strength, and location maintenance capability.

It should be noted that all the sealers, caulks and fillers used in the invention and the application of the invention are non-rigid and compressible. They will however keep each piece of prefabricated shell from resting on an adjacent shell as seen in FIGS. 12 and 13. Since corrosion resistance is important; the sealers, fillers, caulks, and the like are non-corrosive.

FIG. 14 is a cross sectional view of a monolithically poured concrete structure, generally 86, that is shown poured into a prefabricated shell 90. This structure is a shell that is fabricated as set forth above. The column portions 92 extend upwardly from the base portion 94 to the beam portion 96. In a preferred embodiment this shell will be cast as a single piece but may, alternatively be made of several pieces, such as a base piece, the column pieces and the beam piece, each separate but assembled in the field before the now unified shell structure is filled with concrete. It may be desirable to insert metal reinforcement bars into the shell before the shell is filled with concrete. Of course the shell will have the fiberglass or HDPE sheet or panels that will help protect the prefabricated shell from contact with the rebar. The reinforcing bar will end up in the poured concrete and will be sealed from the elements as set forth above. The shell generally 86 may be opened on the bottom of the base portion as shown or a bottom may be cast into the form as a bottom of the base (not shown). Generally, the top of the beam portion is covered with a lid structure (see FIGS. 15 and 16). The advantage of the form structure shown in FIG. 14 is that a single pour can be made to fill the prefabricated shell at the job site. The prefabricated shell 90, (reference character 90 used to show two surfaces of the same shell), will have an exterior surface as shown such as in FIG. 2 as outer layer 12, the sheet of carbon fiber material 20, the spacers or locators 22 and the fiberglass panel 26. Not readily seen in FIG. 14 are the protrusions 28.

FIG. 15 is a cross sectional view of a lid or cap 110 shown expanded away from an open pour element such as 112. Both of these components are prefabricated elements that include the same mix, the enhanced concrete using silica-fume or slag and 4,000 pound concrete, and structural elements as other preformed shells described above (like reference numbers indicate like elements). In the field the cavity of the open pour section 1 12 will be filled, or almost completely filled, with concrete and the lid 110 placed over the cavity of the now filled open pour cavity. Composite dowel rods, such as those shown as 114, will be cast into the lid as shown in FIG. 15. After the pour of concrete into the open pour section 112 the lid will be lowered onto the open element and the dowel rods inserted in the newly filled concrete pour of the section such as 112. In the event that more concrete needs to be added to fill the cavity under the lid, pour openings such as items 124 in FIG. 15 and FIG. 16 may be provided. The pour openings will be used as fill access ports, or, if too much concrete is poured into the cavity and needs to be extruded out of the structure, the pour openings may act as spill ports to allow concrete to flow out of the lidded cavity. In some situations some of the openings will be needed to add concrete while other of the ports or openings 124 will be used to let concrete escape. The pour openings 124 may be sealed after the appropriate concrete fill quantity has been poured into the structure.

A drip edge 114 extends from the edge of the lid to direct water away from the joint between the lid and the open pour section 112. A mastic joint sealer 114 is placed between the lid and the upper edge of the open pour section such that when the lid is placed on the section 112 a seal will be formed through compression of the mastic or compound sealer.

FIG. 16 shows an alternative joint between the lid 118 and the cavity wall 120. In this embodiment a stepped joint 122 is used, either as an alternative to the mastic joint discussed above, or in addition to the mastic joint. That is the step joint may also use mastic to further the efficacy of the seal between the lid 118 and the wall of the open pour section 120.

A summary of the invention is that it is a prefabricated concrete shell that forms a component of a concrete structural element. The prefabricated shell comprises concrete; an additive mixed into the concrete before the concrete is cured; a panel of fluid impervious material forming a surface of the prefabricated shell; a locator extending from the panel of fluid impervious material; and a sheet of mesh fabric spaced apart from the panel. This sheet is located in position by a locator. In one embodiment the additive comprises a reactive pozzolan. This may be what is known as silica fume. In another embodiment the additive can be amorphous silicon dioxide. One advantage of the invention is that the shell, made of concrete with one of the above additives is highly resistant to chloride ion migration and corrosion induced by deicing or marine salts. The mesh fabric used in the shell is a carbon fiber mesh grid while the fluid impervious material comprises a substantially non-metallic membrane. Substantially non-metallic may include having no metallic component at all to the membrane however it is possible that some metallic component can be used as long as there are oxidation minimizing attributes to a membrane having even some metallic content. Similarly the mesh fabric, preferably oxidation resistant, which, in one embodiment is nonmetallic may, in another embodiment, be substantially non-metallic. The mesh fabric will be non-deleterious to the strength of the concrete. The mesh fabric can be fiber mesh, such as but not limited to, a carbon fiber mesh. The prefabricated shell may have a smooth exterior for aesthetic and other reasons. The smooth exterior is formed using a smooth metal form finish to the concrete on the exterior of the prefabricated shell.

The panel of fluid impervious material may be mineral fibers such as fiberglass. It is expected that the panel of fluid impervious material is a water impervious material, which in one embodiment is a 16-ounce/square foot fiberglass panel. The panel of fluid impervious material further comprises a resin coating, such as a polyester based coating. The locators in the structure are preferably nonmetallic but may, in another embodiment be substantially nonmetallic. These locators are positioned between the sheet of mesh fabric and the panel of fluid impervious material. The locators may be attached to the sheet of mesh fabric and to the panel of fluid impervious material as well.

The fabrication of a shell, in one embodiment, is accomplished by performing acts comprising: providing a mold, the mold being a surface wherein the prefabricated shell is molded; providing a panel of fluid impervious material comprising an interior surface; positioning locators proximate the panel of fluid impervious material of the form; providing a sheet of mesh fabric and locating the sheet of mesh fabric proximate the panel of fluid impervious material of the form; placing the panel of fluid impervious material, locators and sheet of mesh fabric in the mold; pouring concrete into the mold, whereby the sheet of mesh fabric and the locators are surrounded by concrete and the concrete contacts the interior surface of the panel of fluid impervious material.

Furthermore the process includes curing the concrete in the mold to form a prefabricated shell. The locators are attached to the fluid impervious material and to the sheet of mesh fabric.

The structure that is formed comprises a prefabricated concrete shell forming a component of a concrete structural element. This prefabricated shell comprises concrete including an additive mixed into the concrete before the concrete is cured; a panel of fluid impervious material forming a surface of the prefabricated shell; a locator extending from the panel of fluid impervious material; a sheet of mesh fabric spaced apart from the panel, the sheet located in position by the locators; a core of concrete located inside the prefabricated concrete shell, the core of concrete adjacent the panel of fluid impervious material, the core of concrete having an additive mixed into the procured concrete, the additive in the concrete being of a lesser amount by percentage than the additive used in the concrete of the prefabricated concrete shell. The additive is silica-fume, a reactive pozzolan, in one embodiment. The additive may be an amorphous silicon dioxide in another embodiment.

Each variation of the invention is limited only by the recited limitations of its respective claim, and equivalents thereof, without limitation by other terms not present in the claim. Likewise, the use of the words “function” or “means” in the Detailed Description of the Drawings is not intended to indicate a desire to invoke the special provisions of 35 U.S.C. 112, Paragraph 6, to define the invention. To the contrary, if the provisions of 35 U.S.C. 112, Paragraph 6 are sought to be invoked to define the inventions, the claims will specifically state the phrases “means for” or “step for” and a function, without also reciting in such phrases any structure, material or act in support of the function. Even when the claims recite a “means for” or “step for” performing a function, if they also recite any structure, material or acts in support of that means or step, then the intention is not to invoke the provisions of 35 U.S.C. 112, Paragraph 6. Moreover, even if the provisions of 35 U.S.C. 112, Paragraph 6 are invoked to define the inventions, it is intended that the inventions not be limited only to the specific structure, material or acts that are described in the preferred embodiments, but in addition, include any and all structures, materials or acts that perform the claimed function, along with any and all known or later-developed equivalent structures, material or acts for performing the claimed function. 

1. A prefabricated concrete shell forming a component of a concrete structural element, the prefabricated shell comprising: a. concrete; b. an additive mixed into the concrete before the concrete is cured; c. a panel of fluid impervious material forming a surface of the prefabricated shell; d. a locator extending from the panel of fluid impervious material; e. a sheet of mesh fabric spaced apart from the panel, the sheet located in position by a locator.
 2. The invention in accordance with claim 1 wherein the additive comprises a reactive pozzolan.
 3. The invention in accordance with claim 1 wherein the additive comprises silica-fume.
 4. The invention in accordance with claim 1 wherein the additive comprises ground granulated blast furnace slag.
 5. The invention in accordance with claim 1 wherein the sheet of mesh fabric is a carbon fiber mesh grid.
 6. The invention in accordance with claim 1 wherein the panel of fluid impervious material comprises a substantially non-metallic membrane.
 7. The invention in accordance with claim 5 wherein the sheet of mesh fabric is nonmetallic.
 8. The invention in accordance with claim 5 wherein the sheet of mesh fabric is oxidation resistant.
 9. The invention in accordance with claim 5 wherein the sheet of mesh fabric is carbon fiber.
 10. The invention in accordance with claim 1 wherein the panel of fluid impervious material is fiberglass.
 11. The invention in accordance with claim 1 wherein the panel of fluid impervious material further comprises a resin coating.
 12. The invention in accordance with claim 1 wherein the locator is nonmetallic.
 13. The invention in accordance with claim 1 wherein the locator is substantially nonmetallic.
 14. The invention in accordance with claim 12 wherein the locator is attached to the sheet of mesh fabric and to a panel of fluid impervious material.
 15. A method of making a prefabricated shell comprising the acts of: providing a mold, the mold being a surface wherein the prefabricated shell is molded; providing a panel of fluid impervious material comprising an interior surface; positioning locators proximate the panel of fluid impervious material of the form; providing a sheet of mesh fabric and locating the sheet of mesh fabric proximate the panel of fluid impervious material of the form; placing the panel of fluid impervious material, locators and sheet of mesh fabric in the mold; pouring concrete into the mold, whereby the sheet of mesh fabric and the locators are surrounded by concrete and the concrete contacts the interior surface of the panel of fluid impervious material.
 16. The method of claim 15 further comprising the act of curing the concrete in the mold to form a prefabricated shell.
 17. The method of claim 15 wherein the concrete comprises reactive pozzolan as an additive to the concrete.
 18. The act as set forth in claim 15 further comprising the acts of connecting a locator to the fluid impervious material and connecting a locator to the sheet of mesh fabric.
 19. A concrete structure comprising; prefabricated concrete shell forming a component of a concrete structural element, the prefabricated shell comprising: concrete including an additive mixed into the concrete before the concrete is cured; a panel of fluid impervious material forming a surface of the prefabricated shell; a locator extending from the panel of fluid impervious material; a sheet of mesh fabric spaced apart from the panel, the sheet located in position by the locators; a core of concrete located inside the prefabricated concrete shell, the core of concrete adjacent the panel of fluid impervious material, the core of concrete having an additive mixed into the procured concrete, the additive in the concrete being of a lesser amount by percentage than the additive used in the concrete of the prefabricated concrete shell.
 20. The invention in accordance with claim 21 wherein the additive is silica-fume. 